Product and method for treatment of soil contaminated with energetic materials

ABSTRACT

Exemplary products and methods are described for in situ treatment of soil that is or may become contaminated with energetic materials or their degradation products. Easily biodegradable organic material and humic material may be distributed on the soil surface in a manner such that portions thereof are carried below the soil surface by infiltrating water, where the easily biodegradable material may be degraded by microorganisms, generating an anaerobic environment suited to further biologic and abiotic reduction of the contaminants, and the humic material may be retained by the soil particles thereby reducing pollutant leaching.

PRIORITY

This non-provisional application claims priority from two provisionalapplications: U.S. Ser. No. 61/421,975 filed Dec. 10, 2010 and U.S. Ser.No. 61/447,676 filed Feb. 28, 2011.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention comprises a product and method for the safe in situtreatment of soil that is or may become contaminated with energeticcompounds or their degradation products, including propellants,explosives, and pyrotechnics that can pose fire or explosion risksduring treatment by other methods.

2. Description of the Related Art

Routine activities at grenade, mortar, artillery, and bombing ranges andopen burn/open detonation (OB/OD) areas often result in accumulation ofresidues of energetic materials in the upper few centimeters of soil.These areas often have disturbed topography with craters, exposed soil,and limited vegetative cover, which increases infiltration and leachingof contaminants. Many energetic materials are weakly bound by soil andcan be transported to groundwater in high permeability soils.

Surface application and tilling of hydrated lime to a depth of sixinches can be effective in reducing leaching of explosives. However,lime treatment has some disadvantages. To be most effective, the limeshould be tilled into the soil. This is a major problem in areas withunexploded ordnance, since disturbing the soil could set off anexplosion, injuring site workers. To apply this technology at mostranges, the unexploded ordnance must be removed from the soil, at aprohibitively expensive cost, before treatment commences. Additionally,in acidic soils containing alumino-silicates and iron hydroxides, largeamounts of lime are required to reach the target pH required foreffective hydrolysis. In humid areas, additional steps must be taken:the alkali is gradually leached out of the surface soil, and additionallime must be applied to maintain performance. The high pH required foreffective treatment will kill most vegetation and is not practical forlarge areas.

In an alternative approach, the surface application of a 10-cm thicklayer of peat moss amended with soybean oil was shown to be effective incontrolling the migration of RDX (Research Department Explosive, RapidDetonation Explosive or Royal Detonation Explosive), from Composition Bdetonation residues. RDX and its breakdown product, MNX, were greatlyreduced after passage through the pilot-scale soil columns. No otherexplosive compounds in the detonation residues were detected in theleachate in over 95% of the aqueous samples collected. Unfortunately,this peat-soybean oil approach had significant operational problems thatmake it impractical for deployment at most ranges and OB/OD areas.Specifically, weapons firing and OB/OD activities can cause the peat tocatch fire. Obviously, an increased fire hazard is not acceptable inthis type of environment. There are also significant questions about thephysical integrity of the peat moss layer and the potential for dustproblems in arid areas. To reduce fire hazard and dust, it is possiblethat the peat-soybean oil layer could be buried. However, burying wouldnot be practical on many ranges due to the very high costs and physicalhazards associated with working in an area with unexploded ordnance.

BRIEF SUMMARY OF THE INVENTION

The present invention comprises a product and method for in situtreatment of soil that is or may become contaminated with energeticmaterials or their degradation products. The method comprisesdistributing easily biodegradable organic material and humic material onthe soil surface in a manner such that easily biodegradable organicmaterial and humic material are carried deeper into the soil byinfiltrating water, thereby enhancing pollutant degradation and/orreducing pollutant leaching, as more specifically described hereafter.

Advantages of the invention will be more fully apparent from thefollowing detailed disclosure made with reference to the Figures, andfrom the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the simulated vertical distribution ofdissolved oxygen in soil with 15 centimeters of biodegradable organicsubstrate and varying substrate decay rate.

FIG. 2 is a graph showing the simulated vertical distribution ofdissolved oxygen in soil treated with varying thickness of biodegradableorganic substrate.

FIG. 3 is a graph showing the substrate decay rate for differentsubstrate thicknesses to generate a minimum dissolved oxygenconcentration of 0.1 milligrams/liter to enhance anaerobicbiodegradation.

FIG. 4 is a graph showing the biochemical oxygen demand (BOD)consumption rate for different substrate thicknesses that will generatea minimum dissolved oxygen concentration of 0.1 milligrams/liter toenhance anaerobic biodegradation.

FIG. 5 shows an exemplary distribution of amendment solution in a 100acre area to be treated.

DETAILED DISCUSSION OF THE INVENTION

The present invention comprises a product and method for treatment ofsoil that is or may become contaminated with energetic compounds ortheir degradation products. The method comprises distributing organicamendments over the soil surface in a manner such that these amendmentsare then carried deeper into the soil by infiltrating water. Forpurposes of this application, “energetic materials” are compounds orformulations with a large amount of stored chemical energy that can berapidly released without an external source of oxygen. The most commonenergetic materials are propellants, explosives, and pyrotechnics,including but not limited to perchlorates, chlorates, nitrates,picrates, dinitrogen tetroxide, nitroaromatics, 2,4,6-trinitrotoluene(TNT), 2,4-dinitrotoluene (2,4-DNT), 2,6-dinitrotoluene (2,6-DNT),triaminotrinitrobenzene (TATB), nitroamines,1,3,5-hexahydro-1,3,5-trinitrotriazine (RDX), and1,3,5,7-tetrahydro-1,3,5,7-tetranitrotetrazocine (HMX),2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane CL-20),nitrocellulose (NC), nitroglycerin (NG), nitroguanidine (NQ),pentaerythritol tetranitrate (PETN), 1,1-diamino-2,2-dinitroethene(DADNE), 2,4-dinitroanisole (DNAN) and nitrotriazalone (NTO).Significant advantages of the teachings herein include: (1) the organicamendments may be spray applied or distributed from a distance, whichreduces the hazard to site workers; and (2) tilling or other disturbanceof the soil, that may expose workers to explosion hazard, is notrequired. Since soil disturbance and unexploded ordnance removal are notpre-requisites to treatment with the inventive method, this method iswell-suited for use at sites such as active weapons ranges where liveartillery is in use on an ongoing basis, and offers significant savingsboth in time and money. Even at range sites no longer in use, or usedonly intermittently, the inventive method is safer and less costly thanprior art methods requiring soil disturbance.

The organic amendments used in this invention consist of easilybiodegradable organic materials and humic materials. For purposes ofthis application, “easily biodegradable materials” are materials whichare fermented by microorganisms in the soil in which they are applied,under anaerobic conditions and, when the pH of the soil is between 5.0and 8.0, release hydrogen and acetate as products of their fermentation.In an exemplary embodiment, these materials are transported at least 10cm into the soil profile by infiltrating water. Transportation of theorganic amendments below the soil surface reduces fire hazards, whichare a major concern in areas receiving energetic materials.Transportation of the organic amendments below the soil surface alsogenerates more strongly anaerobic conditions, which enhances pollutantattenuation and increases the longevity of the amendment.

Below the soil surface, the easily biodegradable material is biodegradedby microorganisms and thereby generates anaerobic conditions thatenhance biological and abiotic reduction of the energetic compounds.

Once anaerobic conditions have been generated in the soil, theseconditions stimulate anaerobic biodegradation of the energetic materialsand reduction of naturally occurring Fe(III) minerals to Fe(II). Theincreased levels of Fe(II) will, in turn, enhance abiotic degradationprocesses. A variety of easily biodegradable materials may be usedincluding, but not limited to, fatty acids, carbohydrates, alcohols, andother soluble organic materials. Desirable materials are low cost, havean aqueous solubility greater than 0.1 grams per gram of water (allowinginfiltration into soil), low volatility (i.e. do not readily evaporateat a temperature less than 40 degrees Celsius and greater than 0.9atmospheres pressure) (reducing air emission), have a flash point above93 degrees Celsius (reducing fire hazards), have a chemical oxygendemand greater than 0.5 gram per gram, and remain effective (i.e., hasnot been entirely depleted and such portion as remains continues tobiodegrade) for more than one month after entering the subsurface of asoil (reducing application frequency).

Glycerol (glycerin) may be particularly useful in this invention as aneasily biodegradable organic material. Glycerol is completely misciblewith water so it can be easily spray applied. The fire hazard forglycerol is classified as low due to its relatively high flash point(176° C., as compared to 17° C. for ethanol) and strongly hygroscopicnature (glycerol will absorb water out of the air). Glycerol has aChemical Oxygen Demand greater than 0.5 grams per gram and iscomparatively long-lived in soil due the limited number of organisms(only Klebsiella, Citrobacter, Enterobacter and Clostridium species)that can ferment glycerol. Other easily biodegradable organic materialsthat may be useful in this invention include soapstock, corn steepliquor, and a wide variety of food processing wastes.

Below the soil surface, the humic material in this embodiment willenhance pollutant retention and reduce pollutant leaching through one ormore of the processes of hydrophobic sorption of energetic material tothe soil, enhanced covalent binding of some pollutants, acting as anelectron shuttle enhancing abiotic degradation by Fe(II), enhancesorption of heavy metals, and providing a reservoir of reducing power tomaintain long-term anoxic conditions.

It is highly desirable that the humic material not only be capable ofspray application but also, after migrating into the soil, and thenattaching to the soil particles as described above, so that itseffectiveness will continue for a longer term than otherwise would bethe case. Humic materials that may be used in this embodiment of theinventive process include: (1) humic acid and humic acid salts (humates)chemically extracted from peat and solid humics; and (2) ligninderivatives (LDs) produced during paper production. In the papermanufacturing process, various chemical processes are used to solublizelignin, forming lignin derivatives (LDs) including: (a) hydrolysislignin produced by strong acid hydrolysis of woody materials; (b) kraftlignin produced through reaction with NaOH and Na₂S; (c) lignosulfonatesproduced through reaction with metal bisulfites and other reagents; and(d) organosolv lignins produced by extraction with ethanol or otherorganic solvents. Hydrolysis and kraft lignins are soluble at high pHbut will precipitate out of solution as the pH is reduced below 8.Lignosulfonates are very soluble and are marketed for a variety ofdifferent uses ranging from dust suppression to emulsification to foodpreparation. There are a variety of lignosulfonates approved by the USFood and Drug Administration (FDA) for direct contact and/orincorporation into food. Lignosulfonates are commonly applied over largeareas (roads, helipads) for dust suppression and to crops to enhancefertilizer adsorption.

To enhance anaerobic biodegradation of energetic materials in soils, thedissolved oxygen (DO) of the soil pore water preferably should bereduced to below 0.1 mg/L. However, DO concentrations depend on the rateof oxygen transport into the soil and rate of oxygen consumption byeasily biodegradable organic material, humic material, and reduced iron.A numerical model has been developed to evaluate the effect of substratedepth and thickness on pore water dissolved oxygen concentrations.Oxygen transport by gas phase diffusion was simulated by finitedifferences. Oxygen consumption was modeled by a dual Monod rateexpression assuming the biochemical oxygen demand (BOD) of the porewater was 5 mg/L or greater wherever substrate was emplaced.

FIG. 1 shows the effect of the substrate consumption rate on thedissolved oxygen (DO) profile in soil where the surface 15 cm of soilhas been treated with biodegradable organic substrate. For this case,the substrate decay rate must be greater than 0.4/d to deduce DOconcentrations to less than 0.1 mg/L.

FIG. 2 shows simulated DO profiles for varying substrate depths andthicknesses when the substrate decay rate is varied to generate aminimum DO less than 0.1 mg/L. The substrate thickness should beselected so the minimum dissolved oxygen concentration is no greaterthan 0.1 mg/L to enhance anaerobic biodegradation. DO concentrationsbelow 0.1 mg/L can be achieved by using organic substrates with highersubstrate decay rates. However, this increases the rate of substrateconsumption and requires more frequent replenishment.

FIG. 3 shows the substrate decay rate used in the FIG. 2 simulations.

FIG. 4 shows the resulting substrate consumption rate for each of theFIG. 2 simulations. When a thin layer of organic substrate is placed onthe soil surface, the DO gradient is very steep, resulting in rapidoxygen transport and requiring a very high substrate decay rate toreduce DO to less than 0.1 mg/L. This high substrate decay rate resultsin rapid consumption of the added substrate and frequent replenishmentto maintain performance, which significantly increases the requiredmaintenance and costs. However, when the substrate is distributed over agreater thickness or placed below the soil surface, the DO gradient isless steep, which reduces the oxygen transport rate and resultingsubstrate consumption rate and thereby reduces maintenance frequency andcosts. The results depicted in FIG. 4 show a clear benefit when theorganic substrate extends from the surface to at least 25 cm below thesurface with the majority of the organic substrate present at a depth ofover 10 cm below the soil surface. The BOD consumption rate is furtherreduced when the substrate amended zone is 50 cm thick and extends from10 to 60 cm below the soil surface.

In the preferred embodiment of this invention, the humic materials aredissolved, suspended, or emulsified in water so as to be transported atleast 10 cm into the soil profile. However once transported below thesurface, the humics must bind to the soil, precipitate and/or attach tothe soil. These objectives can be achieved using several differentapproaches.

In a first approach, humates, hydrolysis lignin, lignosulfonates, andsimilar materials may be easily dissolved in water and spray applied tothe soil surface. Once these materials enter the soil, they will sorb orexchange onto iron oxides and clay particle surfaces and be temporarilyimmobilized. Over time, these materials will be biologicallytransformed, significantly reducing their mobility. Biologicalconversion will be enhanced by the presence of the easily biodegradablematerial, which will generate anaerobic conditions, stimulatingreduction or removal of sulfonate and hydroxyl groups, causing the humicmaterial to be retained by the soil.

In a second approach, kraft lignin (KL), which is soluble at high pH andinsoluble at neutral to low pH, may be used. A KL solution may beprepared at a high pH using a base (e.g., NaOH, KOH, or Ca(OH)₂) and acommercial lignin powder (e.g., Indulin AT from MeadWestvaco), or may bepurchased as an aqueous solution, for example from a paper mill. Thesolution may be applied to the soil surface by spraying and then beallowed to infiltrate. As the high pH solution infiltrates into the soilprofile, the natural acidity of the soil causes the pH to drop and theKL to precipitate on the soil. The depth of KL penetration may beincreased by providing additional base. If desired, KL treatment couldbe combined with surface lime application to treat energetic materialsthrough alkaline hydrolysis, sorption, and biodegradation. In additionto the raw kraft lignins, there are a variety of KLs that have beensulfonated to increase their solubility, generating materials withcharacteristics intermediate between kraft lignins and lignosulfonates.These materials may be dissolved at pH 7-9 but will precipitate when thepH is dropped below 6.

In a third approach, organosolv lignin (OL), which has a low solubilityin water but can be suspended or emulsified using traditionalsurfactants or lignosulfonates, may be used. The emulsion or suspensionmay be applied onto the soil surface by spraying and then be allowed toinfiltrate. As the droplets or particles are transported through thesoil pores, they collide with the soil particles and are retained.

In an exemplary embodiment, an inventive product or products may beprepared containing one or more easily biodegradable organic materialsand humic materials. The products are prepared as a concentrated liquidor dry powder to reduce transportation costs. The products may bepackaged in bags, drums, and totes or delivered in tanker trucks asappropriate. Once delivered to the site, the products are mixed withwater and then spray applied. However in other embodiments, thebiodegradable and humic materials may be delivered and appliedseparately. In some embodiments, sufficient water is added to reduce theviscosity of the mixture to less than 10 centipoise, to aid in sprayapplication and infiltration below the soil surface.

The inventive products may be applied using several differentapplication approaches at sites receiving energetic materials, such asgrenade, mortar, artillery and bombing ranges and open burn/opendetonation (OB/OD) areas. In most cases, the amendments are sprayapplied using a hydroseeder, water cannon, or similar equipment. Inhumid areas, naturally occurring water application (typically, rainfall)may be allowed to infiltrate the amendment into the soil profile. Inmore arid areas, irrigation water may be used to transport the amendmentinto the soil profile. Additional amendments may be periodically appliedto maintain performance. The reapplication frequency to maintain therequisite levels may be determined based on monitoring of small testplots that are near, but not within, the active range.

On small and moderate size ranges, the spray equipment may be located onthe perimeter of the range, outside areas with unexploded ordnance. Thiswould completely eliminate the costs and physical hazards associatedwith personnel entering a range with unexploded ordnance.

On large ranges, narrow corridors may be cleared of unexploded ordnanceto allow installation of distribution pipes. FIG. 5 shows such anembodiment of the inventive process to treat a large range bydistributing the amendment solution over a roughly 100 acre area. Inthis embodiment, three distribution pipes, spaced 700 ft apart, areplaced in the treatment area and connected to a central supply pipe. Theamendment solution may be spray applied throughout the treatment area,using water cannons with a 700 ft radius of influence, for example. Byreducing the area of unexploded ordnance clearance, worker exposure andunexploded ordnance clearance costs are greatly reduced. For the 100acre area shown in FIG. 5, it is anticipated that unexploded ordnanceclearance costs (based on present pricing) would be reduced byapproximately 99%, or $2 million.

On ranges that are routinely cleared, it is likely that only relativelysmall areas around the cleared unexploded ordnance need to be treated.In this case, the explosive ordnance disposal (EOD) team first wouldclear the unexploded ordnance and then would make a single applicationof the amendment in a circle surrounding the former unexploded ordnancelocation. The application radius would be determined based on the sizeand type of ordnance and expected zone of explosive dispersal. Again, ahydroseeder or similar type of equipment may be used to perform theapplication.

The features of the present invention will be more clearly understood byreference to the following examples, which are not to be construed aslimiting the invention.

Example 1 Corn Steep Liquor & Humate

In an embodiment of the inventive process, a dry powder product may beprepared by blending 30% to 70% corn steep liquor powder (available fromQingdao Abel Technology Co., Ltd) and 30% to 70% soluble humates (e.g.,Dry Soluble 80 from Black Earth) and packaged in 20 Kg bags. These bagsmay be transported to a training range where they are stock-piled priorto use. Once the unexploded ordnance is cleared, the EOD team may thenmix one 20 Kg bag per 55 gallon drum of water and spray apply theamendment solution in a circle around the cleared ordnance. The cornsteep and humate is then allowed to soak into the soil, generatinganaerobic conditions, which enhances anaerobic biodegradation andsorption of any explosive residues. Amendment infiltration preferablyshould be concentrated in the bottom of the explosion craters whereresidues are most concentrated.

Example 2 Glycerol & Kraft Lignin

In a second embodiment of the inventive process, a concentrated liquidproduct may be prepared by blending 40% to 60% liquid kraft lignin(e.g., Indulin AT from MWV) and 40% to 60% glycerol, preferably wasteglycerol produced during biodiesel production. The kraft lignin used inthis embodiment is prepared at high pH at a paper mill to keep thelignin in solution. The waste glycerol used in this embodiment has ahigh pH associated with NaOH or KOH carry over from the biodieselproduction process. These materials may be blended and then delivered ina tanker truck for immediate treatment of, for example, a grenade range.At the range, the delivery truck may be parked at the edge of the range.The product may then be pumped directly out of the truck and sprayapplied over the ground surface using a high pressure (e.g., 100-150psi) centrifugal pump. Once application of the concentrated liquidproduct has been completed, sufficient irrigation water may bespray-applied over the surface of the product to carry the product intothe soil . For example, one inch of irrigation water may bespray-applied. In that case, if the soil has a twenty-five percentporosity, one inch of the product as initially applied would saturatefour inches of soil. Once the water application has been completed, thesoil would drain down to field capacity, causing the product to bespread out over the upper eight inches of soil. Application ofadditional water would move the amendment further into the soil. Thistreatment should be sufficient to prevent leaching of explosives togroundwater for one to three years and no clearance of ordnance would berequired.

Example 3 Lignosulfonate

In a third embodiment of the inventive process, unfermented dry powderedlignosulfonates may be obtained containing soluble sugars. The drypowder may be delivered to the OB/OD area, diluted at 1 part powder to 5parts water, and spray applied using, for example, a hydroseeder. If thesoluble sugars are less than 30% by weight, easily biodegradable solubleorganic waste products may be obtained from nearby food manufacturingplants (e.g., whey from dairies, malt from breweries) and spray applied.

The foregoing details are exemplary only. Other modifications that mightbe contemplated by those skilled in the art are within the scope of thisinvention, and are not limited by the examples illustrated herein.

1) An in situ method for reducing contamination caused by energeticmaterial or the degradation products of energetic material, comprising:a. Distributing easily biodegradable organic material and humic materialon top of a soil surface on which energetic materials have been or willbe placed; and b. Applying water to the soil surface, in situ, i. in anamount sufficient to transport at least a portion of the organicmaterial and humic material into the soil and sufficient that, incombination with any naturally occurring water application, the organicmaterial and humic material distributed on top of the soil surface willbe transported at least 10 cm into the soil, and ii. in a manner suchthat after application of the water and the any naturally occurringwater application, the majority of the humic material distributed on topof the soil surface is transported to and retained below the soilsurface. 2) The method according to claim 1, wherein at least a part ofthe water applied to the soil surface contains at least one of theeasily biodegradable organic material and the humic material. 3) Themethod according to claim 1, wherein at least a part of the waterapplied to the soil surface contains both the easily biodegradableorganic material and the humic material. 4) The method according toclaim 1, wherein the humic material is selected from the groupconsisting of sulfonated lignins, hydroxylated lignins, kraft lignins,organosolv lignins, humates, and humic acids. 5) The method according toclaim 1 wherein the humic material consists of kraft lignins andwherein, at the time of distribution, the kraft lignins are in asolution comprising water and at least one base and have a pH greaterthan
 9. 6) The method according to claim 1 wherein the humic materialcomprises a suspension prepared with a surfactant. 7) The methodaccording to claim 1 wherein the humic material comprises an emulsionprepared with an emulsifier. 8) A product for reducing contaminationcaused by energetic material or the degradation products of energeticmaterial, comprising one or more compositions in the form of at leastone of a liquid, an emulsion, or a suspension, where said compositioncomprises, in combination: a. At least one easily biodegradable organicmaterial; b. At least one humic material; and c. Water, 9) The productof claim 8 wherein the at least one easily biodegradable organicmaterial comprises a material with a solubility of at least 0.1 gram pergram of water. 10) The product of claim 8 wherein at least one of the atleast one easily biodegradable organic materials is selected from thegroup consisting of fatty acids, carbohydrates, alcohols, and othersoluble organic materials. 11) The product of claim 8 wherein at leastone of the at least one easily biodegradable organic materials isselected from the group consisting of glycerol, soapstock, corn steepliquor, and food processing wastes. 12) The product of claim 8 whereinat least one of the at least one easily biodegradable organic materialsis selected from the group of materials having the followingcharacteristics: a. water solubility greater than 0.1 gram per gram, b.low volatility, c. flash point above 93 degrees Celsius, d. chemicaloxygen demand greater than 0.5 gram per gram, and e. remain effectivemore than one month after entering the subsurface of a soil. 13) Theproduct of claim 8 wherein the at least one easily biodegradable organicmaterial comprises glycerol. 14) The product of claim 13 wherein theglycerol comprises a byproduct of biodiesel production. 15) The productof claim 8 wherein the at least one humic material comprises at leastone of sulfonated lignins, hydroxylated lignins, kraft lignins,organosolv lignins, humates, and humic acids.